We propose to study the thermodynamic details of reactions between oXygen and carbon monoxide and hemoglobin M Iwate. The object of our work will be to measure the change of enthalpy and entropy of the ligand reactions with the two hybrid species alpha Mmet beta met deoxy and alpha 2 Mmet beta 2 deoxy under conditions of different pH and in the presence and absence of 2,3-diphosphoglycerate. The entropy changes of these reactions can be determined from the combination of enthalpy measurements using gas microcalorimeter and equilibrium constants as measured by Gersonde (Aachen). The M Iwate hemoglobin molecule is considered to be a frozen T- state configuration but still shows a high degree of cooperativity for the two step reaction with the alpha2Mmet beta2 deoxy species. A primary goal of this work will be to determine whether cooperativity is associated with large differences in entropy and enthalpy values even though the molecule retains its T-state. The work will be in collaboration with Professor Gersonde, who has studied the reaction properties of these materials and has offered to supply the needed samples for calorimetric work. A special gas microcalorimeter will be built, based on our present microcalorimeter design, to handle small samples and to follow the carbon monoxide and oxygen reaction as a function of extent of reaction.